Experimental Investigation of a Planar Liquid Film Atomization Under High-Speed Gas Stream

We present a systematic experimental investigation of the primary breakup of a planar liquid film subjected to high-speed co-flowing gas streams. A water film of thickness D_ℓ ≈ 150 μm is produced from a symmetric airfoil lip and sheared on both sides by compressed air. Interfacial dynamics were recorded with a high-speed camera and analyzed to extract transverse wavelengths, rupture modes, and their dependence on operating conditions. We find that the transverse wavelength λ_tra decreases strongly with increasing gas speed and that, for a given dynamic pressure ratio M = (ρ_gV²_g )/(ρ_ℓV²_ℓ ), different absolute combinations of V_g and V_l produce markedly different λ_tra. These observations indicate that gas-shear intensity and the gas flow instability modes (vortex shedding) control the breakup of the liquid film; the liquid inflow plays a secondary role under our conditions. The results provide experimental benchmarks for model validation and suggest routes to tune atomizer performance via gas-side control.